I'm been struggling to find a perfect resolution/refresh rate for my HTPC (without success) and it made me think; why do LCD monitors need a specific refresh rate?

I understand why CRT's had specific timings, and this has obviously carried over to the new generation of TV's.

But theoretically it should be possible to design a system where a device 'posts' an image to a digital screen whenever it wants to, and the screen shows that image until it gets another.

There would obviously be issues and limitations with doing this, but there could be some pretty major bonuses:

a bluray player could output at whatever FPS it wanted, 24, 25, 29.97, 60..

games could have the best of both worlds - Vsync without the framerate penalty, a frame would be rendered as soon as it is finished. I don't know if this would cause jerkyness though because every image could take a slightly different time to render, but it sounds good in theory! Also, if the screen required Xmilliseconds to present an image, then this could also cause problems if the game could render more quickly, but i'm sure there would be solutions.

The marketers could call it 'Native FPS' or something.